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Date: Mon, 16 Apr 2018 17:25:14 +0200 From: Joerg Roedel <joro@...tes.org> To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>, "H . Peter Anvin" <hpa@...or.com> Cc: x86@...nel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org, Linus Torvalds <torvalds@...ux-foundation.org>, Andy Lutomirski <luto@...nel.org>, Dave Hansen <dave.hansen@...el.com>, Josh Poimboeuf <jpoimboe@...hat.com>, Juergen Gross <jgross@...e.com>, Peter Zijlstra <peterz@...radead.org>, Borislav Petkov <bp@...en8.de>, Jiri Kosina <jkosina@...e.cz>, Boris Ostrovsky <boris.ostrovsky@...cle.com>, Brian Gerst <brgerst@...il.com>, David Laight <David.Laight@...lab.com>, Denys Vlasenko <dvlasenk@...hat.com>, Eduardo Valentin <eduval@...zon.com>, Greg KH <gregkh@...uxfoundation.org>, Will Deacon <will.deacon@....com>, aliguori@...zon.com, daniel.gruss@...k.tugraz.at, hughd@...gle.com, keescook@...gle.com, Andrea Arcangeli <aarcange@...hat.com>, Waiman Long <llong@...hat.com>, Pavel Machek <pavel@....cz>, "David H . Gutteridge" <dhgutteridge@...patico.ca>, jroedel@...e.de, joro@...tes.org Subject: [PATCH 26/35] x86/mm/pti: Clone CPU_ENTRY_AREA on PMD level on x86_32 From: Joerg Roedel <jroedel@...e.de> Cloning on the P4D level would clone the complete kernel address space into the user-space page-tables for PAE kernels. Cloning on PMD level is fine for PAE and legacy paging. Signed-off-by: Joerg Roedel <jroedel@...e.de> --- arch/x86/mm/pti.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c index f967b51..60a1ee0 100644 --- a/arch/x86/mm/pti.c +++ b/arch/x86/mm/pti.c @@ -348,6 +348,7 @@ pti_clone_pmds(unsigned long start, unsigned long end, pmdval_t clear) } } +#ifdef CONFIG_X86_64 /* * Clone a single p4d (i.e. a top-level entry on 4-level systems and a * next-level entry on 5-level systems. @@ -371,6 +372,25 @@ static void __init pti_clone_user_shared(void) pti_clone_p4d(CPU_ENTRY_AREA_BASE); } +#else /* CONFIG_X86_64 */ + +/* + * On 32 bit PAE systems with 1GB of Kernel address space there is only + * one pgd/p4d for the whole kernel. Cloning that would map the whole + * address space into the user page-tables, making PTI useless. So clone + * the page-table on the PMD level to prevent that. + */ +static void __init pti_clone_user_shared(void) +{ + unsigned long start, end; + + start = CPU_ENTRY_AREA_BASE; + end = start + (PAGE_SIZE * CPU_ENTRY_AREA_PAGES); + + pti_clone_pmds(start, end, _PAGE_GLOBAL); +} +#endif /* CONFIG_X86_64 */ + /* * Clone the ESPFIX P4D into the user space visible page table */ -- 2.7.4
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